Technical Reports do not necessarily represent final EPAdecisions or positions. They are intended to present technicalanalysis of! issues using data which are currently available. Thepurpose infc-the* release of such reports is to facilitate theexchange o£ technical information and to inform the public oftechnical developments which may form the basis for a final EPAdecision, position, or regulatory action.

The attached report entitled "Cold Starting an Alcohol-FueledEngine with Ultrasonic Fuel Atomization," EPA/AA/TDG/93-02,presents the test results of an engine modified to be cold startedwith the assistance of automatically controlled ultrasonic fuelatomizers and run on methanol fuel. This report represents thesuccessful completion of an international cooperative program; theeffective development of improved alcohol fuel cold starttechnology by the Japanese government and industry, and theassociated technical evaluation by the U.S. government.

A test program was devised at EPA's National Vehicle and Fuel Emissions Laboratory to evaluate a Tonen ultrasonic fuel atomizer system on a Honda B20 engine using both M85 (85% methanol, 15% hydrocarbons) and M100 (neat methanol) fuels to determine whether cold starting a premixed-charge port injected engine on alcohol fuels at low ambient temperatures can be improved. [1] Modification to the engine's intake manifold was performed at the Japanese Automotive Research Institute (JARI) in cooperation with the New Energy Development Organization (NEDO) to install heated injectors in close proximity to the ultrasonic atomizers. The engine is also equipped with the stock port injector system intact and functional. Successful M100 cold starts were obtained down to 20°F (-7°C).

II. Introduction

Tonen initially developed the ultrasonic fuel atomizer in the mid-1980's to investigate the relationships between spark ignition characteristics and combustion stability in gasoline-fueled race car engines. After Tonen achieved some success in this development program, a representative of EPA visited Tonen in November of 1988 to negotiate a cooperative agreement for the development of the ultrasonic atomizer as a cold start assist device for pre-mixed charge alcohol-fueled engines.

Since the cooperative agreement involved working with the U.S.•government, the Tonen Corporation aligned itself with the New Energy Development Organization (NEDO) and the Japanese Automotive Research Institute (JARI) to take advantage of the testing facilities and related research expertise already in existence within the Japanese government.[2] What resulted was a three year development program between these Japanese organizations with periodic meetings to update the EPA on the status of their progress. At first, it was planned to adapt the ultrasonic atomizer syatea to a Toyota engine, but ultimately it was decided to instead, UM a Honda B20 four cylinder engine.

Ill* Svat+M Description

By trial and error, JARI engineers evaluated various different intake manifold locations to mount two of these atomizers in order to realize the best possible charge distribution to the four cylinders, with the minimum amount of distance and wall surface area between the ultrasonic atomizers and the cylinders. The final design featured a distance of roughly 6 inches (15 cm) between the ultrasonic atomizers and a nearly 90° elbow, followed by an<xref image="9100RS4N.TIF|V3|2011:01:26:04:52:47.00|67986|0"> image: </xref>------- -2-

approximately 8 inch (20 cm) distance between the elbow and thecylinders (see Appendix A). This is not exactly an optimumconfiguration, but is probably the best geometry given theconstraints of the engine's intake manifold design.

Throughout its development program/ Tonen continued to refinethe design of the ultrasonic atomizer. At first it was merely aprobe which, when energized, vibrated ultrasonically in the intakeair stream between the port fuel injectors and the combustionchambers. Then the injectors were mounted in the same holder asthe atomizers, such that the fuel stream leaving the injectorbecame excited by the atomizer before it made its way into theintake air stream. Next, Tonen fitted the atomizer/injectorassembly with an electrically heated glow plug. Three differentheated atomizer configurations were tested.[3]

The first of these heated atomizer configurations (Type A) isshown in Figure 1. In this design, the fuel is supplied close tothe base of the glow plug, such that the fuel has to travel thelength of the glow plug before being introduced near the tip of theultrasonic atomizer, thereby adding as much heat to the fuel aspossible before exciting it with the atomizer.

The second atomizer configuration tested (Type B) is shown inFigure 2. In this version, the length of the glow plug isshortened, and the glow plug is fitted with an insulating shieldand a preheat zone. The fuel is introduced closer to the tip ofthe glow plug into the preheat zone, where it first has to travelback toward the base of the glow plug over a greater surface area Ultrasonic Atoaiier Design*

to promote heat transfer between the fuel and the hot surface,before being introduced to the atomizer. This design also shieldsthe glow plug from being quenched by the direct flow of the fuelspray.

The third and final heated atomizer configuration (Type C) issimilar to the second version with the addition of stainless steelbeads at the tip of the glow plug (Figure 3). Tonen found that theaddition of these beads provides an additional surface between theglow plug and the atomizer, which retains heat and transfers it tothe fuel. The improvement in fuel atomization is significantenough to justify this subtle difference in the design of theheated injector/atomizer assembly.

The final ultrasonic atomizer system design consists of two ofthese Type C glow plug heated injector/atomizer assemblies mountedon the intake manifold of the Honda B20 engine. The system iscontrolled by a Pantos Nippon Denshi Kagaku (NDK) Sofrecs 8604ASuper Intelligent Data Logger/Analyzer with an AU-1208 signalconditioner. This unit is connected to a switching box withcontrol of the glow plug heater, ignition and the engine's starter.Engine control parameters are traced and are monitored on a PantosNDK Model LCD-8660 Color Display Unit. Power is supplied to theseunits by two Pantos NDK Model AC-8600 Power Supply Units. Anoscilloscope is used to insure that injection events occurproperly. Exhaust mixture concentration is sensed by four lambdasensors, one in each exhaust bank, and monitored by four Horiba AirFuel Ratio Analyzers Model MEXA-l10(lambda). SPRAY Pre-h«at zont

The engine used for this test program is a 1991 Honda B20,such as is used in the Honda Prelude, a water cooled in-line fourcylinder engine with a displacement of 2.0L modified for use ofneat methanol (M100) and methanol/hydrocarbon blends such asM85.[4] The engine is equipped with four stock port fuel injectorsin addition to the two temperature controlled electrically operated"cold start" injectors mounted in the ultrasonic atomizerassemblies. Engine compression ratio is 10.5:1 and ratedhorsepower is 135 @ 5800 rpm.

IV. Starting Procedure

Prior to each starting attempt, the battery, an InterstateDeep Cycle SRM-24 marine battery with 550 cold cranking amps, ischarged at a slow rate overnight until fully charged. The engineis placed in the cold room and soaked at the desired testtemperature overnight, or until the oil temperature is within + or- one degree centigrade of the desired test temperature. A flowchart for the starting procedure employed in this test program isshown in Appendix B.

Initially, control of injection is selected between thechoices of manual and automatic. The main injection system, basedon the stock Honda gasoline engine maps, was automaticallycontrolled throughout this test program. The ultrasonic atomizerinjectors were also automatically controlled throughout the testprogram, but are based on methanol engine maps developed at JARI.Also prior to a cranking attempt, the fuel control system isswitched on and the injection triggering mechanism is checked forproper operation. Injection events are then verified by thepresence of a waveform on the oscilloscope.

The ignition switch is then turned to the on position suchthat the glow plug heaters can be energized prior to cranking. Theheaters are thus enabled for the desired glow plug preheat time, aperiod of 10 seconds per NEDO recommendation, and if sampling foremissions, the CVS is turned on and a sampling bag is initiated.NEDO recommended the 10 second preheat time, because fueltemperature is not significantly increased after 10 seconds asshown in Figure 4.

The engine is then cranked by flipping a starter switch andholding it: in the on position for an increment of 10 seconds andthen letting go. If the engine starts, the cranking time isrecorded, and the engine is run at idle for five minutes todetermine the idle emissions (g/min) until the engine is warmed up.If the engine does not start, the heater remains on, but thestarter switch is allowed to automatically flip back to the offposition for a waiting period of 10 seconds to protect the starterfrom overheating. After 10 seconds, the starter switch is turnedback to the on position to crank the engine for another 10 seconds.If the engine does not start after six of these cranking andwaiting periods, (i.e., after 120 seconds) it is determined that<xref image="9100RS4Q.TIF|V3|2011:01:26:04:52:51.00|76815|0"> image: </xref>------- -5' 100

the engine is not startable at the temperature being tested withinreasonable commercial acceptability.

Once the engine does start, the starter switch is let go (andautomatically flips back to the off position), and the glow plugheater switch is also turned off. At the end of a test, e.g.,"after a five minute emission sample is taken, the ignition switchis turned off, and the STOP button on the fuel control system ispressed to terminate the logging of engine control parameter data.V.Teat Results The results obtained from this test program are quite similarto the result* obtained by the JARI engineers in Japan before theengine wa* shipped to the EPA for evaluation. [5] The heated ultra-sonic atoadies system helped to improve the cold startability ofboth MlOfr and M8S fuels at colder temperatures than normallyobserved fro» unassisted engines with only OB injection systemsusing these fuels. Th* engine is capable of being cold started onM100 at temperatures as low as 20T (-7»C) with a glow plug preheattime of 30 seconds. The engine is capable of being cold started onM85 without the ultrasonic atomizer system at ambient temperatureslower than are capable of being obtained in EPA's current cold roomtest facility.

The engine was initially tested on 11.8 RVP M85 fuel at 50»F (10°C). Startup was almost instantaneous, with a required cranking<xref image="9100RS4R.TIF|V3|2011:01:26:04:52:52.00|45174|0"> image: </xref>-------time of only 1.1 second. The cold engine idle speed was 1620 rpm,though after five minutes of operation, this speed was reduced to1340 rpm. Average lambda values in the four exhaust runners were0.84, and were quite stable except for cylinder No. 1 which wassomewhat leaner at 0.94. Only the OEM injectors were required tostart the engine. The ultrasonic atomizor injection system was notrequired, nor was the glow plug preheater. Figure 5 shows both theJARI and the EPA test results on both M85 and M100.

Testing continued on M85 fuel, and cold starting was success-ful at 32°F (0°C), 15°F (-10°C), and 9°F (-13eC) . The resultsclosely matched the results obtained at the JARI. Cranking timeincreased to 3.5 seconds at the 9°F (-13°C) test temperature, andidle engine speeds increased to 1800 rpm initially and 1400 rpmafter 5 minutes of stabilizing. Average lambda values were similarto the 50°F (10°C) test except during the 9«F (-13«C) test wherelambda values averaged a relatively rich 0.71, with cylinder No. lsomewhat leaner at 0.77. Again, only the OEM injection system wasrequired to start the engine. The cold start injectors, atomizersand preheaters were not required for any test using M85 fuel withinthe lower temperature limit of the cold room used in this testprogram.

The engine oil and coolant were checked between each test, andthe battery was fully charged before each starting attempt. Aftercompleting the MBS evaluations, the engine's fuel was drained andtesting was initiated on M100 fuel.

The M100 fuel used has an RVP of 4.6 psi. The first test onM100 was performed at 50°F (10°C). Testing with M100 required theuse of not only the OEM injectors, but also the heated cold startatomized fuel injectors. Preheat time at this temperature was 10.seconds. Cranking time to start was 5.5 seconds, and initialengine speed was 1622 rpm. Lambda values with M100 were leanerthan with M85, and averaged 0.96. Cylinder No. 1 demonstrated alambda value of 1.1. This cylinder, due to the placement of thetwo ultrasonic atomizers, was consistently the leanest throughoutall tests of both fuels.

The cold room temperature was cooled to 20°F (-7°C), and acold start attempt was made with the use of the ultrasonic atomizerfuel injectors and the same glow plug preheat time of 10 seconds.The engine would not start under these conditions under theprescribed-cranking procedure. This same result occurred in theJARI tests, and it was decided to lengthen the glow plug preheattime before attempting another 20°F (-7°C) or colder test.

First, however, a test was run at 32°F (0°C) in an effort tocorrelate data at other points along the curves already generatedat the JARI laboratory. The engine started with the ultrasonicinjectors and the 10 second glow plug preheat time after 28 secondsof cranking. Engine speed was slightly higher than observed duringthe 50°F (10°C) test, with an initial speed of 1650 rpm and astabilized speed of 1400 rpm after 5 minutes.<xref image="9100RS4S.TIF|V3|2011:01:26:04:52:54.00|79141|0"> image: </xref>------- -7- 60 50o0)w0)s£ e. cd• J-.o 40 30 20 10 M85 — MI+US without heater EPA results T M85 OEM A M100 MI + US with heater

Two more tests were run at the intermediate temperatures of 40°F (4°C) and 35°F (2°C) with the ultrasonic atomizer injectors and a glow plug preheat time of 10 seconds. Cranking times for successful starts were 11 and 14 seconds, respectively. Again, the results closely matched the results obtained at the JARI laboratory. However, lambda values, for some unknown reason, were considerably richer during the 40°F (4°C) test, averaging 0.73 compared with lambda values averaging 0.96 at 35°F (2°C). This anomaly, along with the highly variable meter readings, caused some skepticism with regard to the accuracy of the air/fuel ratio measurements. During engine operation after these two successful cold starts, engine speed was initially about 1700 to 1775 rpm, and 1265 to 1400 rpm after 5 minutes.

The test cell was then cooled to 25°F (-4°C) and the lower limit of cold startability of the ultrasonic atomizer system on M100 was again investigated. This time the atomizer injectors were used with a glow plug heatup time of 30 seconds instead of only 10 seconds. Though NEDO found that the fuel temperature does not increase measureably after 10 seconds, it was decided to evaluate whether a longer preheat time added more heat to the system for improved cold start performance. The engine started after 49 seconds of cranking. Lambda values were relatively lean, and averaged near stoichiometric levels of 0.96. Engine speed was elevated, however, with an initial post startup measurement of 2200 rpm and a stabilized level of over 1600 rpm after 5 minutes.

Another 20°F (-7°C) start attempt was made, this time with an extended glow plug preheat time. The preheat time in this case was 30 seconds as in the successful 25°F (-4°C) test. By the prescribed starting procedure, the engine did not start within the acceptable cranking time limit. After an additional waiting period with the heater still on, the engine finally did start, but this'test would be considered a "no start1* condition within the prescribed starting procedure or within reasonable commercial acceptability. No emission samples were measured following the successful 20°F (-7°C) N100 test, though levels would be expected to be high given the excessive cranking time.

During: most other successful cold starts on either M85 or M100, emissions were sampled as the engine warmed up under idle condition*; for a period of five minutes starting with the initial cranking period (i.e., coincident with turning the starter switch on) and ending five minutes later. As a result, the emissions of tests with short cranking times are generally less than those of tests with long cranking times, because a larger percentage of the emissions are collected while the engine is running and fuel is being burned more completely. Table 1 shows the post-start idle emissions of the test engine. Data points are not included in Table 1 for the successful cold starts on N85 at 50°F (10°C) and on M100 at 20°F (-7°C), because emissions were not sampled during these tests. The emissions of the engine on both fuels are, as expected, higher, and the cranking times are longer, at colder temperatures. .<xref image="9100RS4U.TIF|V3|2011:01:26:04:52:57.00|86197|0"> image: </xref>------- -9- Table i

Honda B20 Cold start Idle Emissions (g/min)FuelTemp (°F)NOXHC"C02COM85320.030.675922.8150.031.426529.690.041.656631.3M100500.020.32606.3400.030.40615.3350.040.65707.9320.041.706511.3250.111.85819.821*---- **Engine did not start at 21°F on M100 with a 10 second preheattime. No emission samples were obtained.

HC emissions not adjusted for methanol fuel. Exhaust HCdensity assumed equal to that of gasoline = 16.33 g/ft3.VI • Conclusions and Successful cold starts on M100 fuel with a heated ultrasonic fuel atomizer system were obtained down to 20 °F (-7°) with a 30 second glow plug preheat period. With only the NEOO recommended 10 second preheat time, successful M100 cold starts were obtained at temperatures as low as 32°F (0°C) .

Cold starting the engine on M85 does not require the use of the ultrasonic atomizer system or the glow plug heater at'-temperatures as low as 9°F, or the lower limit of the EPA cold test facility utilized in this test program. Successful cold starts were obtained on N85 with less cranking time than is required with only the stock fuel injection system.

EPA and JARI data of measured cranking times on N100 with the heated ultrasonic atomizer system, and on M85 with and without the ultrasonic atomizer and the glow plug heater, are in close agreement » •- ---".•^ T--*W The cold start performance on M100 is similar to results obtained with long duration spark systems evaluated previously at the EPA. [6]

The proximity of the ultrasonic atomizer system to the engine combustion chambers is not optimum. In particular, the near 90° elbow in the intake manifold makes it difficult for finely atomized fuel to reach the combustion chambers without condensing on the manifold wall and generating larger fuel droplets, especially at low ambient temperatures.<xref image="9100RS4V.TIF|V3|2011:01:26:04:52:58.00|54250|0"> image: </xref>------- -10-

Tonen engineers investigated the optimum glow plug preheattime, and found very little benefit in fuel temperature increase isobtained with preheat times longer than 10 seconds. Heat retentionof the fuel (and M100 cold start performance) was found to improvewith glow plug preheat times of up to 30 seconds, but the detrimentto glow plug durability of these extended preheat times is unknown.

EPA was not able to test the effects of variation in ignitiontiming, ignition duration, ignition energy, or injection quantityon cold start performance of M85 and M100 with the ultrasonicatomizer system. These parameters were fixed throughout thisevaluation program.

The accuracy of relative air fuel ratio measurements was notdetermined and is, therefore, unknown.

Cold start performance of an alcohol-fueled engine equippedwith the ultrasonic fuel atomizer system in combination with longduration spark or plasma ignition systems, and perhaps variablecontrol of ignition and injection parameters, is likely to promoteimproved alcohol engine cold start performance, and is worthy offurther investigation.(7]

VII. Acknowledgments

The authors wish to acknowledge the efforts of NEDO, JARI, andTonen managers and engineers for providing system development,operation, maintenance, and troubleshooting functions throughoutthis international cooperative development program.

Maybe some of you remember what I told few years ago about fuel droplet size affecting ethanol cold start.We had setup where gasoline was injected into engine intake manifold through small volume wide angle full cone misting/fogging nozzle, during cold cranking. We used one setup with gear pump at pressure about 4 bar and another with vibration pump (so called ULKA pump from expresso coffe machine) at pressure close to 20 bar. At 20 bar fluid pressure, nozzle gave very fine fog like cloud at open space and at 4 bar more like mist with droplets. When testing these setupes at real world conditions 20 bar version gave much better cold start results. Cranking time was shorter and less attemptes to start engine where needed.